Roll control system, device and method for controlling vehicle stability

Abstract

A roll control system for a vehicle is disclosed. The roll control system includes front and rear stabilizer bars, first and second magnetorheological actuators, and an electronic control system. The first magnetorheological actuator is disposed between the front stabilizer bar and the front suspension on one side of the vehicle, and a first droplink is disposed between the front stabilizer bar and the front suspension on the other side of the vehicle. The second magnetorheological actuator is disposed between the rear stabilizer bar and the rear suspension on one side of the vehicle, and a second droplink is disposed between the rear stabilizer bar and the rear suspension on the other side of the vehicle. The electronic control system is responsive to a vehicle operating characteristic and is in signal communication with the first and second magnetorheological actuators. The first and second actuators are responsive to a control signal from the electronic control system such that they are locked in response to the vehicle undergoing a cornering maneuver, and are unlocked in response to the vehicle not undergoing a cornering maneuver.

1. A roll control system for a vehicle having a front suspension and a rear suspension, the roll control system comprising:
 a front stabilizer bar; 
 a rear stabilizer bar; 
 a first magnetorheological actuator disposed between the front stabilizer bar and a support portion of the front suspension on one side of the vehicle, and a first droplink disposed between the front stabilizer bar and the front suspension on the other side of the vehicle; 
 a second magnetorheological actuator disposed between the rear stabilizer bar and a support portion of the rear suspension on one side of the vehicle, and a second droplink disposed between the rear stabilizer bar and the rear suspension on the other side of the vehicle; and 
 an electronic control system responsive to a vehicle operating characteristic and in signal communication with the first and second magnetorheological actuators; 
 wherein the first and second actuators are responsive to a control signal from the electronic control system such that they are locked in response to the vehicle undergoing a cornering maneuver, and are unlocked in response to the vehicle not undergoing a cornering maneuver; and 
 wherein in response to either of the first and second magnetorheological actuators being locked, an end of the respective stabilizer bar connected thereto is restrained from translational movement in a direction defined by an axis of the respective magnetorheological actuator. 
 
     
     
       2. The roll control system of  claim 1 , wherein:
 the first droplink is a third magnetorheological actuator; and 
 the second droplink is a fourth magnetorheological actuator; 
 wherein the third and fourth actuators are responsive to a control signal from the electronic control system such that they are locked in response to the vehicle undergoing a cornering maneuver, and are unlocked in response to the vehicle not undergoing a cornering maneuver. 
 
     
     
       3. A magnetorheological actuator, comprising:
 first, second and third portions; 
 the first and second portions disposed having a translational degree of freedom with respect to each other; 
 the third portion having a rotational degree of freedom with respect to the first and second portions; 
 the first and third portions coupled via a translation-to-rotation converter; 
 the second and third portions coupled via a magnetorheological fluid; and 
 a magnetic field generator in field communication with the magnetorheological fluid; 
 wherein the third portion is rotationally responsive to translational motion between the first and second portions, and the shear stress characteristic of the magnetorheological fluid is responsive to the magnetic field generator, such that a rotational braking action of the third portion results from field excitation at the magnetic field generator; 
 wherein in response to field excitation at the magnetic field generator, the first and second portions are restrained from having translational motion relative to each other in response to a first axial load between the two portions; and 
 wherein in response to no field excitation at the magnetic field generator, the first and second portions are allowed to have translational motion relative to each other in response to a second axial load between the two portions. 
 
     
     
       4. The actuator of  claim 3  wherein:
 the first portion comprises a tube having a ball nut; 
 the third portion comprises a shaft having a ball screw at one end and a magnetic rotor ring at an opposing end, the ball screw engagingly disposed at the ball nut, the magnetic rotor ring disposed within the magnetorheological fluid; and 
 the second portion comprises a housing receptive of the ball nut, the shaft and the magnetic field generator. 
 
     
     
       5. The actuator of  claim 3 , wherein:
 the second portion comprises two concentric cylindrical surfaces defining an annular space therebetween, the magnetorheological fluid being disposed within the annular space; and 
 the third portion comprises a cylindrical magnetic rotor ring disposed within the fluid within the annular space. 
 
     
     
       6. The actuator of  claim 5 , wherein the third portion comprises a middle section made of substantially non-magnetic material. 
     
     
       7. The actuator of  claim 5 , wherein the annular space is sized to contain equal to or less than about 50 cubic centimeters of the magnetorheological fluid. 
     
     
       8. The actuator of  claim 7 , wherein the annular space is sized to contain equal to or less than about 10 cubic centimeters of the magnetorheological fluid. 
     
     
       9. The actuator of  claim 3 , wherein:
 the first axial load is equal to or less than about 6 kilo-Newtons; and 
 the second axial load is equal to or greater than about 20 Newtons. 
 
     
     
       10. A stabilizer control system for a vehicle having a suspension with a stabilizer bar and a support, the stabilizer control system comprising:
 a plurality of sensors responsive to at least one operating characteristic of the vehicle; 
 a controller responsive to signals from the plurality of sensors; and 
 a magnetorheological actuator disposed between the stabilizer bar and the support, the actuator comprising: 
 first, second and third portions; 
 the first and second portions disposed having a translational degree of freedom with respect to each other; 
 the third portion having a rotational degree of freedom with respect to the first and second portions; 
 the first and third portions coupled via a translation-to-rotation converter; 
 the second and third portions coupled via a magnetorheological fluid; and 
 a magnetic field generator in field communication with the magnetorheological fluid; 
 wherein the third portion is rotationally responsive to translational motion between the first and second portions, the shear stress characteristic of the magnetorheological fluid is responsive to the magnetic field generator, and the magnetic field generator is responsive to an activation signal from the controller; 
 wherein the magnetorheological actuator is responsive to the controller such that an activation signal from the controller causes an increase in the shear strength of the magnetorheological fluid, a rotational braking action at the actuator, and translational motion restraint between the stabilizer bar and the support. 
 
     
     
       11. The system of  claim 10 , wherein:
 the plurality of sensors comprises a vehicle speed sensor, a steering angle sensor, and a lateral accelerometer; and 
 the activation signal is active in response to the vehicle speed being equal to or greater than a first threshold value, and at least one of the magnitude of a steering angle change from a neutral position being equal to or greater than a second threshold, and the magnitude of the vehicle lateral acceleration being equal to or greater than a third threshold. 
 
     
     
       12. The system of  claim 11 , wherein:
 the activation signal is active in response to the magnitude of a steering angle change from a neutral position being equal to or greater than a second threshold, and the magnitude of the vehicle lateral acceleration being equal to or greater than a third threshold. 
 
     
     
       13. The system of  claim 10 , wherein:
 the second portion comprises two concentric cylindrical surfaces defining an annular space therebetween, the magnetorheological fluid being disposed within the annular space, the annular space being sized to contain equal to or less than about 10 cubic centimeters of the magnetorheological fluid; and 
 the third portion comprises a cylindrical magnetic rotor ring disposed within the fluid within the annular space. 
 
     
     
       14. The system of  claim 10 , wherein:
 in response to field excitation at the magnetic field generator, the first and second portions are restrained from having translational motion relative to each other in response to a first axial load between the two portions, the first axial load being equal to or less than about 6 kilo-Newtons; and 
 in response to no field excitation at the magnetic field generator, the first and second portions are allowed to have translational motion relative to each other in response to a second axial load between the two portions, the second axial load being equal to or greater than about 20 Newtons. 
 
     
     
       15. A method of controlling a vehicle stabilizer system, the system comprising a plurality of sensors responsive to at least one operating characteristic of the vehicle, a controller responsive to the sensors, an actuator responsive to the controller and disposed between a first part and a second part of the vehicle suspension, the method comprising:
 receiving at the controller a signal from the plurality of sensors; 
 analyzing the sensor signal and generating an activation signal in response thereto; and 
 activating the actuator in response to the activation signal so as to cause a braking action at the actuator and restraint of motion between the first and second parts of the vehicle suspension; 
 wherein the plurality of sensors comprises a vehicle speed sensor, a steering angle sensor, and a lateral accelerometer, the method further comprising: 
 generating the activation signal in response to the vehicle speed being equal to or greater than a first threshold value, and at least one of; the magnitude of a steering angle change from a neutral position being equal to or greater than a second threshold, and the magnitude of the vehicle lateral acceleration being equal to or greater than a third threshold. 
 
     
     
       16. The method of  claim 15 , wherein the actuator is a magnetorheological actuator comprising:
 first, second and third portions; 
 the first and second portions disposed having a translational degree of freedom with respect to each other; 
 the third portion having a rotational degree of freedom with respect to the first and second portions; 
 the first and third portions coupled via a translation-to-rotation converter; 
 the second and third portions coupled via a magnetorheological fluid; and 
 a magnetic field generator in field communication with the magnetorheological fluid; 
 the method further comprising: 
 increasing the shear strength of the magnetorheological fluid in response to the activation signal; 
 restraining rotational motion between the second and third portions of the actuator; and 
 restraining translational motion between the first and second portions of the actuator. 
 
     
     
       17. The method of  claim 16 , wherein the restraining translational motion further comprises:
 restraining translation motion between the first and second portions of the actuator in response to an axial load between the two portions being equal to or less than about 6 kilo-Newtons.